Image analysis often requires a determination of whether an observed point source object is a single object or whether it is made up of several overlapping or blended objects. When objects in an image are spaced closer together than the resolving power of the optics, several closely spaced objects can erroneously appear as one large object.
Software exists to process electronic (i.e., digitized) representations of images. The processing includes operations performed on the digital image data to effectively increase the resolution of the image and attempt to minimize or eliminate image artifacts. An example is a software application called Source Extractor, which is used to process and deblend astronomical images. Deblending is the process of attempting to determine whether an observed object is a single object or a collection of closely-spaced, but separate objects.
Deblending in Source Extractor is performed by examining an intensity profile of the objects appearing in an image and comparing that profile to a threshold. This is described in, for example, B. W. Holwerda, Source Extractor for Dummies 32-34 (Space Telescope Science Institute, Baltimore, Md.) and also in E. Bertin, SExtractor v2.3 User's Manual 20-22 (Institue d'Astrophysique & Observatoire de Paris). This technique in accordance with the Rayleigh criterion is generally unable to resolve individual objects that are closer than about 1.5 times their full-width half-max (FWHM). FWHM is an important measure of the quality of an imaging device and its spatial resolution. If the distribution is Gaussian, then the FWHM can be calculated as FWHM=2*{square root over (−2*log(0.50σ))}, where σ is the standard deviation, or the square root of the variance. FWGM is also the bandwidth of the system. The Rayleigh criterion is the generally accepted criterion for the minimum optically resolvable detail.